Lighting device

ABSTRACT

The invention relates to a lighting device, comprising a light guide ( 11; 31; 43 ), a light source ( 12; 32, 33; 41 ), which couples the light that is emitted into the light guide, and a support ( 10; 20, 21; 22, 23; 30, 35, 38; 40, 42 ) in the form of a shell, consisting of several interconnected sub-shells which enclose the light guide, at least in the area in which the light should be deviated. The invention also relates to a method for producing a lighting device.

[0001] The invention relates to an illumination arrangement having anoptical waveguide, a light source, which couples emitted light into theoptical waveguide, and having a mount for the optical waveguide.

[0002] Arrangements of this type, in which a light-emitting diode or alaser diode is often used as light source, have applications in generalillumination or as background illumination for liquid-crystal displays(LCD). In this case, the optical waveguide performs the function ofguiding the light which is emitted by the light source and is coupledout from the optical waveguide at the end of the optical waveguide or ata window provided for this. The surface of the optical waveguide isstructured for this purpose in the window region, e.g. by knobs,grooves, or by some other roughening in order to homogenize the lightexit The optical waveguides are composed of transparent material, forexample epoxy resin or polymethyl methacrylate (PMMA). In the course ofguiding the light and its necessary deflection in the optical waveguide,on the one hand the light lost must be as little as possible, and on theother hand cost-effective production and also practical and simpleassembly must be possible.

[0003] In the exemplary embodiment shown in FIG. 5, a light-emittingdiode 50 couples its light into an optical waveguide 51 plugged into amount 52 a, 52 b. The mount 52 and the light-emitting diode 50 aremounted on a printed circuit board (PCB) 53. The light emitted by thelight-emitting diode 50 is deflected at a bevel 54 of the opticalwaveguide by total reflection. For production engineering reasons, inparticular in favor of ease of assembly, the bevel 54 is not coveredwith a reflective material. During the deflection of the light at thebevel 54, which is angled by preferably 45°, light necessarily emergesfrom the optical waveguide. which light is lost for the envisagedapplication purpose since it is not guided any further in the opticalwaveguide. On the other side, the mounts 52 a, 52 b simultaneously serveas reflectors which prevent light from emerging from the opticalwaveguide 51 on these sides. When observing the surface of the opticalwaveguide from the direction B, for example when the optical waveguideis embodied as LCD background illumination, some regions on the opticalwaveguide surface appear brighter than others (hot spots) as a result ofthe light deflection at the boundary surface 54 and the direct radiationof the light source. Hot spots are bright surface regions which appearin light exit window and cannot be corrected by the surfaceconfiguration of the optical waveguide in the light exit window.Producing a special reflector for the inclined surface 54 in the form ofan injection-molded part seems to be too costly, on the other hand, onan industrial scale since it is too expensive overall.

[0004] The invention is based on the object of specifying anillumination arrangement of the type mentioned in the introduction and amethod for producing it by means of which an improvement is madepossible in a cost-effective manner.

[0005] The invention achieves this object by means of the features ofpatent claims 1 and 14. Refinements of the invention are characterizedin subclaims.

[0006] The invention is described below using exemplary embodimentswhich are illustrated in the figures of the drawing, in which;

[0007]FIG. 1 shows a diagrammatic cross section through an illuminationarrangement according to the invention,

[0008]FIG. 2 shows side views of a mount for the optical waveguide

[0009]FIG. 3 shows a diagrammatic cross section of a special embodimentof the invention,

[0010]FIG. 4 shows a further, partially perspectively illustratedembodiment of the invention, and

[0011]FIG. 5 shows a diagrammatic cross-sectional illustration ofpreviously used illumination arrangements.

[0012]FIG. 1 shows an illumination arrangement 1 in a cross-sectionalillustration. The arrangement comprises a mount 10 or an opticalwaveguide 11, into which one or more light sources 12 a, 12 b feedlight. The light sources 12 are preferably light-emitting diodes (LED)or laser diodes, but other light sources such as incandescent lamps arealso possible. The light source 12 and the mount 10 are mounted on aprinted circuit board 14. The mount 10 surrounds the optical waveguide11 in shell form in the regions in which the light has to be deflectedand guided. In order to introduce the optical waveguide into the shell,and to be able to mount it, the mount 10 is formed from a plurality ofshell elements. In the example of FIG. 1, the mount 10 contains on itstop side a window 13 through which an observer B can observe the opticalwaveguide or the light can be coupled out. The window 13 in the mount 10is configured in such a way that the illumination arrangement can serveas an element of background illumination for liquid-crystal displays.

[0013] In accordance with FIG. 1, the mount 10 for the optical waveguide11 simultaneously has the main function of a reflector with thereflector surfaces 16 a, 16 b, with the aid of which the light beams canbe deflected without relatively large light losses arising. Thedeflection angle is inherently arbitrary, but 90° here. Depending ontechnical requirements and specifications, the optical waveguide 11 withthe mount 10 is constructed in such a way that the optical losses and/orthe hot spots are minimized. The mount 10 is shaped in the lightdeflection region and in the window region 10, such that light canemerge diffusely through the window 13. The upper reflector surface 16 acan be multiply angled or rounded. With respect to the opticalwaveguide, the lower reflector surface 16 b is convexly formed orexpanded in order that light cannot emerge in a concentrated manner atone location. Both, the optical waveguide 11 and the mount 10 can beproduced as injection-molded parts. Transparent material, e.g. PMMA, isused as the optical waveguide. The mount 10 is typically opaque to lightand reflective at its inner surfaces in order to reflect back into theoptical waveguide the light which emerges at the deflection points ofthe optical waveguide.

[0014] According to the invention, the mount 10 is designed in shellform and contains at least two shell elements. FIG. 2 shows a side viewof the arrangement in accordance with FIG. 1 from viewing direction A.In accordance with FIG. 2a), the mount contains for the opticalwaveguide two shell elements 20 and 21, which are designed largelysymmetrically with respect to the central line. In the light propagationdirection, the optical waveguide has a largely rectangular crosssection. During assembly, the optical waveguide is firstly introducedlaterally into one of the two shell elements 20 or 21 and then enclosedby the other half-shell 21 or 20, respectively, at the regions not yetprotected.

[0015] The two half-shells 20 and 21 are connected by a snap-actiondevice 25, 26. In this case, a lug 25 fixed to the half-shell 21 andhaving an opening is pushed over a knob 26 fixed to the other half-shell20. However, the two half-shells can also be connected in any other formwhich ensures that the two half-shells enclose the optical waveguide. Inaddition to a releasable connection such as that using the snap-actiondevices 25, 26, fixed connections, for example by bonding, are alsoappropriate. In order to prevent the situation where gaps arising at theabutting edge of the two half-shells 20 and 21, possibly due to materialtolerances or due to an aging behavior, lead to the coupling-out oflight, it is possible to fold the two shell elements 20 and 21 at theirabutting edge, so that the shell elements overlap at the fold and becomeoptically opaque.

[0016]FIG. 2b shows another arrangement for the two shell elements. Inthis case, the optical waveguide is firstly introduced from the sideinto a shell element 22, which encloses the optical waveguide to anextent such that only a cover 23 has to be laterally emplaced in orderto enclose the optical waveguide in the light-guiding region. In thisexemplary embodiment, the connection between the shell elements 22 and23 is effected by a plurality of snap-action devices 27, 28. Projectingknobs are arranged on the shell element 22 and the openings in the lugs28 can latch into said knobs. The advantage of this arrangement is thereleasibility of the mount arrangement. It goes without saying that, inan embodiment of FIG. 2a, too, the shell elements 22 and 23 can beprovided with a fold, so that no light can emerge at the abuttingsurface.

[0017] In the arrangement in accordance with FIG. 1, it is possible tofeed in light from only one light source 12. Preferably, however, aplurality of light sources 12 a, 12 b are provided, which, as in FIG. 1,feed light into the optical waveguide from both sides. What is more,further light sources may be arranged perpendicularly to the plane ofthe drawing. This makes it possible to observe a high light intensity atthe window 13. With the arrangement in accordance with FIG. 1, it ispossible for the light that is to be coupled out, or the observationwindow 13, to be arranged remote from the light source 12. The opticalwaveguide 11 and the shell mount 10 can be produced extremely favorablyby virtue of the production of injection-molded parts, at the same timethe light guidance by virtue of the form of the optical waveguidechannels and of the shell mount designed as reflectors being effected sooptimally that a maximum of light can be utilized for the illuminationpurposes The construction in the form a bridge means that it is possibleto produce extremely space-saving arrangements because, below the mount10 in the free space toward the circuit board 14, further components 15can be arranged on the circuit board.

[0018]FIG. 3 shows a partial cross section of a further embodiment ofthe invention. This provides a shell-type mount 30 for the opticalwaveguide 31, which in this case are mounted by their side 38 in aplanar manner on the circuit board 34. In contrast to FIG. 1, thearrangement contains not only an upwardly radiating LED 32 but a chamber36 separated from the latter by a partition 35, arranged in whichchamber is an LED or laser diode 33 radiating sideways over the edges.In this construction, a bridge arrangement as illustrated in FIG. 1 isnot provided. The advantage of the arrangement in accordance with FIG. 3is that the optical power coupled into the optical waveguide can beconsiderably higher than in the case of the arrangement in FIG. 1. Here,too, the inner surfaces 37 of the mount 30 serve as reflectors.

[0019]FIG. 4 shows a further, partially perspective exemplary embodimentof the invention, in which the shell elements of the mount are notseparated vertically, as illustrated in FIG. 2, but horizontally. Inthis embodiment, the optical waveguide 43 is plugged into the lowershell element 40 from above and subsequently covered by the upper shellelement 42. The lower shell element is mounted on the PCB 45. The uppershell element can be connected to the lower shell element in the mannerdescribed with reference to FIG. 2. In the exemplary embodiment, 3 LEDs41 a to 41 c are provided on each circuit-board side of the opticalwaveguide, but there may also be more or fewer individual light sources.

[0020] Furthermore, there are a multiplicity of possibilities forproducing optical waveguides and associated shell elements which enablevirtually arbitrary variation for the coupling-in and coupling-out oflight. This is because the optical waveguides are largely completelycovered by the beam type mount, except for the coupling-in andcoupling-out regions, the inner surfaces of the mount serving asreflector surfaces,

1. An illumination arrangement having an optical waveguide (11; 31; 43),a light source (12; 32, 33; 41), which couples emitted light into theoptical waveguide, and having a mount (10; 20, 21; 22, 23; 30, 35, 38;40, 42), which is formed as a shell from a plurality of shell elementswhich are connected to one another and enclose the optical waveguide atleast in regions in which the light is intended to be deflected.
 2. Theillumination arrangement as claimed in claim 1, characterized in thatthe inner walls of the shell elements are designed as reflectors (16;37; 44).
 3. The illumination arrangement as claimed in claim 1 or 2,characterized in that the at least one shell element has a light exitopening (13).
 4. The illumination arrangement as claimed in one of thepreceding claims, characterized in that the mount for the light holderis constructed from two shell elements (20, 21; 22, 23; 40, 42).
 5. Theillumination arrangement as claimed in one of the preceding claims,characterized in that the shell elements contain a vertical orhorizontal abutting edge and/or an overlapping fold.
 6. The illuminationarrangement as claimed in one of the preceding claims, characterized inthat the shell elements (20, 21) abut one another approximatelycentrally with respect to the optical waveguide and are constructedessentially symmetrically.
 7. The illumination arrangement as claimed inone of patent claims 1 to 5, characterized in that the shell elements(22, 23) contain a part (22) which accommodates the optical waveguideessentially on three sides and can be closed off by a side wall (22). 8.The illumination arrangement as claimed in one of claims 1 to 5,characterized in that the shell elements (40, 42) contain a base part(40) and a cover (42).
 9. The illumination arrangement as claimed in oneof the preceding claims, characterized in that the optical waveguide andthe shell elements of the mount are designed as shaped parts andcoordinated with one another in such a way that the light-guiding lossesand/or bright surface regions (hot spots) are minimal.
 10. Theillumination arrangement as claimed in one of the preceding claims,characterized in that the shell elements can be connected to one anotherby releasable elements (25, 26; 27, 28).
 11. The illuminationarrangement as claimed in one of the preceding claims, characterized inthat the light source is a light-emitting diode (LED) or a laser diode,above which the mount for the optical waveguide is arranged and whichcouples the emitted light directly into the optical waveguide.
 12. Theillumination arrangement as claimed in one of the preceding claims,characterized in that a plurality of light sources (41 a, 41 b, 41 c; 12a, 12 b) are provided.
 13. The illumination arrangement as claimed inone of the preceding claims, characterized in that the mount (30, 35,38) is constructed in such a way that it can accommodate a vertically(12; 32; 42) and/or horizontally (33) emitting light source.
 14. Amethod for producing an illumination arrangement as claimed in one ofpatent claims 1 to 13, characterized in that an optical waveguide (11;31; 43) is firstly inserted into one shell element (20; 22; 40) and isthen covered by a further shell element (21; 23; 42).
 15. The method asclaimed in claim 14, characterized in that the optical waveguide and theshell elements are produced as injection-molded parts.
 16. The method asclaimed in either of claims 14 and 15, characterized in that the mountwith the inserted optical waveguide are connected to a circuit board(14; 34; 45) in such a way that these are arranged above a light sourcewhich is electrically supplied via lines on the circuit board.
 17. Themethod as claimed in claim 13 or 14, characterized in that firstly alower part (40) of the mount for the optical waveguide is connected to acircuit board (45) above a light source (42), in that the opticalwaveguide (43) is then introduced into the lower part (40), and in thata cover (40) is subsequently placed onto the lower part and the opticalwaveguide and connected to the lower part (40).